Abnormal stereotyped behaviors are a prominent aspect of the behavior of mentally retarded, blind and autistic children and adults. The origins of these behaviors are not yet clear but they may be homologous to some normal infant behaviors. Several short-term observational and experimental studies are proposed to investigate the factors which originate and maintain body, hand and object stereotypes in 2-5 year old children. Another study with young infants will determine whether abnormal behaviors emerge from normal patterns and will apply the results of the previous studies in the series in an attempt to prevent the maintenance of the behaviors in the infant's behavior repertoire.